The invention is directed to fluid mechanics and more particularly to the design of a curved intake duct through which fluid flows, for example, a reciprocating internal combustion engine of the spark ignition type.
It has long been known that the power which can be delivered by any engine in which fuel is burned with air is limited by the rate at which it can take in air, combine it with fuel, and exhaust the products. The key to high sustained power output and reduction of contaminants in combustion products is easy breathing.
Some of the energy released from the fuel on combustion has to be used to pull air in and to push combustion products out. The smaller the amount of energy required, obviously, the greater will be both the useful work available and the efficiency of the engine.
The prior art teaches that the most efficient curved intake ports for reciprocating internal combustion spark ignited engines must follow rigid principles. Those principles require that the radius of the surface or floor of the bend of the curved portion of the port must have a constant bend radius, and be adequately large and there must be no discontinuities therealong. A radius of about one quarter of the port diameter is desirable and the unobstructed area of the passage should be increased in the region of the valve guide or stem and its surrounding boss to an area greater than that at the exit from the bend. The latter principle improves the basic flow pattern within the curved duct, it reduces the turbulence of flow over obstructions, and it leads to a more uniform flow toward the outlet which has the effect of reducing the turbulence wake produced by the valve stem, guide and base. Any deviations from these fixed and long time relied on principles of intake ducts supposedly reduces the efficiency of the internal combustion engine to which they are installed.
Most of the commonly known intake ducts to which the invention may be directed are far from the above described "ideal" for a number of reasons at least two of which are economics and convenience.
With the ideal above identified intake duct in mind any improvements thereto which would be inexpensive and convenient to utilize would be widely accepted in this art.